Help

Hi, I have a dll in C++, and i try to use fortran for some calculation to test if the speed could be improved. i wrote a DLL in fortran(using plato3 and ftn95) but i got a problem during building the project(in C++), i got messages like this one: ustTest.lib(test.obj) : error LNK2001: unresolved external symbol ___CHECK95

i'm not sure that the probleme is in the dll!!!may be some one has any idea :roll:

i'm new in Fortan. PS:sorry for my bad english.

FTN95 comes with a C++ compiler called SCC.

If your C++ code will compile with SCC then this is the simplest way to mix C++ and FTN95 Fortran. Then you can link using SLINK.

Otherwise it is not easy to mix the two languages.

When using a third party compiler you also have to consider which calling convention is being used. By default FTN95 does not use STDCALL.

I'm using VC6(visual studio) like that:

extern 'C' double BZ_Y(Points* bz,double x);

void test() { Points* bz = new Points[4]; double x = 0.1; x = BZ_Y(bz,x); delete[] bz; }

; double x = 0.1; x = BZ_Y(bz,x); delete[] bz; }

[quote:d93f72fe74="PaulLaidler"]FTN95 comes with a C++ compiler called SCC.

If your C++ code will compile with SCC then this is the simplest way to mix C++ and FTN95 Fortran. Then you can link using SLINK.

Otherwise it is not easy to mix the two languages.

When using a third party compiler you also have to consider which calling convention is being used. By default FTN95 does not use STDCALL.

here is my code: first file:

module Bezier
	type Point
		double precision x,y
	end type

	CONTAINS
         ......
	double precision function Get_t(bz,x)
	.....
        end function	
end module

the second file:

	double precision function Bz_Y(bz, x)
    	use  Bezier
    	....
	end function

i found something similar here with compaq fortran, so i corrected my C++ code like that

extern 'C' 
{
	double __declspec(dllimport) __stdcall BZ_Y(Points* bz,double x); 
}
 
void test()
{
	Points* bz = new Points[4];
	double x = 0.1;
	x = BZ_Y(bz,x);
}

and now i have just one link error:

(http://www.thescripts.com/forum/thread280324.html) with compaq fortran, so i corrected my C++ code like that

extern 'C' 
{
  double __declspec(dllimport) __stdcall BZ_Y(Points* bz,double x); 
}
 
void test()
{
  Points* bz = new Points[4];
  double x = 0.1;
  x = BZ_Y(bz,x);
}

and now i have just one link error:

[quote:f5593af1c5]Inter29.obj : error LNK2001: unresolved external symbol __imp__BZ_Y@12

i tried to put

	double precision function Bz_Y(bz, x)
        	!DEC$ ATTRIBUTES DLLEXPORT::Bz_Y
 		!DEC$ ATTRIBUTES C, ALIAS: 'BZ_Y@12':: Bz_Y
		use  Bezier
        end function

but it does not work 😢

it seems that the problem is in how to make the function [color=red:f5593af1c5]Bz_Y[/color:f5593af1c5] exported as [color=red:f5593af1c5]BZ_Y@12[/color:f5593af1c5]

As I said, the simplest way forward is to compile your C++ with SCC. Have you tried this?

Quoted from PaulLaidler As I said, the simplest way forward is to compile your C++ with SCC. Have you tried this?

i didn't try this, but i'm afraid that, it will be more complicated to make changes in my C++ code, i'm not sure that codes are compatible between VC++6 and SCC???

i will try this, but i want to understand what is wrong or how to resolve the problem.

If you post very short but complete C++ and Fortran sample code then I may be able to help you with the details.

Use just a few lines of code. Compile your C++ using a Microsoft C++ compiler. Compile your Fortran using FTN95. Use SLINK to link. Provide details of all the compiler and linker command lines.

thanks for your help.

Quoted from PaulLaidler If you post very short but complete C++ and Fortran sample code then I may be able to help you with the details.

Use just a few lines of code. Compile your C++ using a Microsoft C++ compiler. Compile your Fortran using FTN95. Use SLINK to link. Provide details of all the compiler and linker command lines.

code for test

INTEGER(KIND=3) FUNCTION FuncInteger() 
FuncInteger = 347 
END FUNCTION 

c++ part:

extern 'C' int __declspec(dllimport) __stdcall FUNCINTEGER(); 
void test()
{
	int x = FUNCINTEGER();
	x++;
}

with Slink i got:no main, WinMain or LibMain function

with the linker of VC6 i got Inter29.obj : error LNK2001: unresolved external symbol __imp__FUNCINTEGER[color=red:2d7529c5df]@0[/color:2d7529c5df]

In the Salford ftn95 user guide in page 167 'Generation of DLLs and exporting of functions' i found this:

The export command

The export command has the form: export entryname [=internalname] [@ordinal [noname]] [data]

i added

F_STDCALL INTEGER(KIND=3) FUNCTION FuncInteger()  ALIAS 'FUNCINTEGER@0'
FuncInteger = 347 
END FUNCTION 

but the problem is still there

Quoted from PaulLaidler FTN95 comes with a C++ compiler called SCC. If your C++ code will compile with SCC then this is the simplest way to mix C++ and FTN95 Fortran. Then you can link using SLINK.

my code didn't compile with SCC :roll:

i found a solution, with calling to LoadLibrary and GetProcAddress in VC.

There is an example of how to call VC DLLs from FTN95 (and how to call FTN95 DLLs from VC) in the examples installed with FTN95.

Quoted from Andrew There is an example of how to call VC DLLs from FTN95 (and how to call FTN95 DLLs from VC) in the examples installed with FTN95.

i tried to use the same thing but it doesn't work

Have you specifically looked at the two example programs contained in:

c:\program files\silverfrost\ftn95\demo\win32\visualcinteroperability

and

c:\program files\silverfrost\ftn95\demo\win32\visualcinteroperability2

These are provided as Visual Studio projects and with batch files for compilation. These certainly do work (at least for Visual Studio 7.1 upwards).